We Should Stop Citing the Case-Lethality Rate for COVID-19—or Start Using it for Influenza

The CDC estimates that, for the 2019-2020 flu season (last surveillance point was April 4, from the end of September), there were 39 million flu illnesses. The number of positive tests for the flu was 291,241. I will refer to positive tests as flu cases. That’s quite a discrepancy. I explain this in a moment.

The CDC attributes 24,000 deaths to the flu so far this season. That’s a case-lethality rate of 9.7%, or roughly one dead for every ten persons who test positive—a shocking statistic. However, on the basis of the estimated number of actual illnesses, the death rate is 0.75%, or less than one in a hundred.

The multiple used this year to estimate actual cases from positive cases is a factor of 134. There are complex reasons why this number is utilized and you can read about the mathematical models used to make the estimate in the following CDC page: https://www.cdc.gov/flu/about/burden/how-cdc-estimates.htm. The model was developed because epidemiologists are aware that far fewer cases are confirmed by testing than actually exist in the population.

There are 675,243 confirmed cases of and 34,562 deaths from COVID-19 so far. That is a case lethality rate of 5.1%, or roughly half the case lethality rate for the flu based on confirmed cases. However, we must keep in mind that the CDC does not report case lethality rate for the flu. It uses the epidemiological estimates to calculate the death rate.

Applying the same extrapolation as applied by the CDC to flu illnesses this year yields 106 million COVID-19 illnesses. That would put the death rate at 0.63% from COVID-19. Again, the lethality of the SARS-CoV-2 virus is less than that of influenza.

Now, it is unlikely that 106 million Americans have had or currently have COVID-19. I am only applying the multiple to raise the issue about reporting of relative risk.

Consider that he standard estimate for asymptomatic and mild (cold-like) cases is around 80%. Accepting that number, that still represents 21 million flu-like illnesses from SARS-CoV-2. That still seems like a large number (and this would have implications for the degree of herd immunity discussed in my previous podcast). If It is possible that either asymptomatic and mild cases are a greater percentage of the total number of cases or the multiple is smaller for COVID-19 than it is for the flu. But the question we should be asking is why has no multiple been applied to COVID-19 at all?

The comeback will likely be that we don’t yet have the experience with this virus to know to approximate that number, but we surely know the number is significantly greater than zero. If 80% have no symptoms or only mild symptoms, then the majority of cases are not being tested. And there are many with severe cases that are to tested. These obvious facts should be communicated clearly by authorities and the media. All reporting about deaths should emphasize this point.  

Or to put this another way, we might ask why there is a multiple applied in the case of flu illnesses. My guess is that, at least in part, a one-out-of-ten case-lethality rate for influenza would provoke calls for social distancing, sheltering-in-place, and quarantine for the flu, and that would make normal life impossible. Smartly, an epidemiological model is applied to reduce the rate of death from the illness.

But the problem here should be obvious. The authorities and the media are comparing apples to oranges—and they are doing so in a direction that makes COVID-19 seems much more deadly than the flu. To be sure, COVID-19 is deadly. It may very well be more deadly. But how much more deadly? For sure, it is not nearly as deadly as the case-lethality rate makes it appear since it is obvious that most cases of SARS-CoV-2 infection are unreported, whereas dead bodies from flu-like viruses rarely go unreported (at least not for long). (And we have seen authorities including the COVID-19 death counts bodies that have not tested positive for SARS-CoV-2.)

We need authorities to come clean on this discrepancy. Not being clear about the relative risks of COVID-19 over against the flu feeds the panic exploited by the federal and state and local governments to justify the sharp and unprecedented curtailment of freedom and democracy. It appears that they have manufactured the panic.

Published by

Andrew Austin

Andrew Austin is on the faculty of Democracy and Justice Studies and Sociology at the University of Wisconsin—Green Bay. He has published numerous articles, essays, and reviews in books, encyclopedia, journals, and newspapers.

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